The rarity of crystals depends entirely on the context of the word “crystal.” Scientifically, the crystalline structure is one of the most common organizational forms of matter, making most crystals ubiquitous in the world. However, if the question refers to the flawless, large, and chemically pure specimens prized as gemstones, the answer shifts dramatically toward extreme scarcity. To understand true rarity, it is necessary to separate the common structural definition from the highly specific conditions that produce a valuable mineral specimen.
Defining the Crystalline Structure
The scientific definition of a crystal centers on its internal architecture: an ordered, repeating, three-dimensional arrangement of atoms, molecules, or ions. This periodic structure is known as a crystal lattice, which extends throughout the material in a systematic way. Unlike amorphous solids, such as glass, crystalline materials exhibit long-range order. This highly organized atomic arrangement gives crystalline solids distinct physical properties, including a sharp, specific melting point and the tendency to break along flat surfaces called cleavage planes. The repeating pattern within the lattice dictates the external geometric shape of the crystal when it is allowed to grow freely.
The Ubiquity of Crystalline Materials
When defined by their internal structure, crystalline materials are fundamental to nearly all solids on Earth, and the vast majority of minerals making up the planet’s crust and mantle are crystalline, including quartz, feldspar, and calcite. Common household substances, such as table salt and sugar, are also crystalline solids. The ordered lattice structure is characteristic of almost all metals, including gold, iron, and copper, which are composed of millions of tiny crystalline grains. Furthermore, ice is a molecular crystal with a hexagonal lattice structure. Crystalline silicon is the foundation of the electronics industry because its defined structure allows for precise control of electrical conductivity.
Factors That Determine True Rarity
The extreme rarity of certain crystals, such as diamonds or rubies, is not due to the scarcity of the crystalline structure, but the highly demanding conditions required to produce a perfect specimen. Rarity in the gemological sense is a combination of geological scarcity and exceptional quality. A crystal becomes truly rare when it achieves the specific combination of chemical purity, size, and clarity needed for a flawless gemstone. Geological formation conditions must be precise, often involving high pressure, high temperature, and extremely slow growth rates over millions of years. Trace elements, which create the vivid colors in a gem, must occur in exact concentrations; for example, chromium creates the deep red color in a ruby. Most crystals formed in nature contain internal imperfections, known as inclusions, or are too small to be valuable, meaning rarity increases exponentially when a crystal is large, highly transparent, and possesses no visible flaws.